Driven by a desire to use polysaccharides in various applications, researchers have explored for polysaccharides that are biodegradable and that can be made economically from renewably sourced feedstocks. One such polysaccharide is alpha-1,3-glucan, an insoluble glucan polymer characterized by having alpha-1,3-glycosidic linkages. This polymer has been prepared, for example, using a glucosyltransferase enzyme isolated from Streptococcus salivarius (Simpson et al., Microbiology 141:1451-1460, 1995). Also for example, U.S. Pat. No. 7,000,000 disclosed the preparation of a spun fiber from enzymatically produced alpha-1,3-glucan.
Various other glucan materials have also been studied for developing new or enhanced applications. For example, U.S. Patent Appl. Publ. No. 2015/0232819 discloses enzymatic synthesis of several insoluble glucans having mixed alpha-1,3 and -1,6 linkages. Large soluble glucans, such as those having a high percentage of alpha-1,6 linkages, have also been enzymatically synthesized (e.g., U.S. Patent Appl. Publ. No. 2016/0122445). Various enzymatic synthesis routes are disclosed in International Patent Appl. Publ. Nos. WO2015/183721, WO2015/183724, WO2015/183729, WO2015/183722, WO2015/183726 and WO2015/183714 for producing small soluble glucan materials suitable for use in dietary and other applications.
While these and other advances have been made in producing glucan polymers using glucosyltransferase enzymes, less attention appears to have been drawn to improving the glucan yields of such enzymes. Addressing this technological gap, disclosed herein are glucosyltransferases engineered to have modified amino acid sequences endowing these enzymes with enhanced glucan production properties.